1. Field of the Invention
This invention relates to a demagnetizing power source used for demagnetizing a magnetized substance by a loop damping demagnetization technique.
2. Description of the Prior Art
In known demagnetizing power source of the foregoing type, the constant voltage direct current output of a rectifying circuit is supplied to an exciting coil through a polarity changing-over circuit having a pair of relays. Operation of this polarity changing-over circuit was conventionally controlled by a limit switch for controlling the energization of these relays and a rotary cam for controlling the turning-on/off of the limit switch or by a switch mechanism consisting of a rotary disk having a conductive strips attached and divided circumferentially and a brush making contact with the rotary disk. Prior art disclosing use of a rotary disk is typified by U.S. Pat. No. 3,164,753.
However, the control of the change-over cycle by the rotor of the rotary cam or rotary disk type can not change over the polarity of current supplied to the exciting coil with high speed and thus a satisfactory demagnetizing effect cannot be obtained. Also with such prior power sources, pattern of change-over cycle is determined by the rotary cam or rotary disk each formed with conductive strips; and, consequently dispersion occurs due to the accuracy of finishing said rotary cam or rotary disk, thereto resulting in dispersion of the demagnetizing effect. Further, in order to change the change-over cycle to have high demagnetizing effect in such prior power sources, the rotary cam or rotary disk needs to be replaced so that the pattern of change-over cycle is not easily accomplished.